KR20160131027A - Method for producing polarizing plate - Google Patents

Abstract

A first step of bonding a protective film to one side of a polarizing film through an aqueous adhesive layer and laminating a release film on the other side of the polarizing film through a layer made of a volatile liquid, And a second step of drying the layer and volatilizing the volatile liquid.

Description

METHOD FOR PRODUCING POLARIZING PLATE [0002]

The present invention relates to a method for producing a polarizing plate in which a protective film is bonded to one surface of a polarizing film.

The polarizing plate is widely used as a polarizing light supplying device in a display device such as a liquid crystal display device and also as a polarizing light detecting device. As the polarizing plate, a protective film is generally bonded to a polarizing film using an adhesive.

Various types of polarizer plates capable of realizing this have been proposed in accordance with the market demand for lighter polarizer thin films. One of the typical examples thereof is a one-side polarizer polarizer in which a protective film is bonded to only one side of the polarizer film -109860 (Patent Document 1)).

Patent Document 1: JP-A-2009-109860

In producing a one-side protective polarizing plate, a protective film is bonded to one side of the polarizing film through an adhesive layer, and a peelable releasing film is laminated on the other side of the polarizing film to which the protective film is not bonded. It is common to stack them on the other side. This peeling film is peeled off in a subsequent step such as a step of bonding the one-side protective polarizing plate to, for example, a liquid crystal cell.

However, in the conventional method for producing a single-side polarizing polarizing plate, wrinkles are generated in the peeling film when the temperature in the drying step after bonding the protective film to the polarizing film with an adhesive is high, There is a problem that the film is broken.

Accordingly, an object of the present invention is to provide a method capable of producing a one-side protective polarizing plate while suppressing the breakage of the polarizing film.

The present invention provides a method for producing a polarizing plate described below.

A first step of bonding a protective film to one side of a polarizing film through an aqueous adhesive layer and laminating a releasing film on the other side of the polarizing film through a layer made of a volatile liquid,

A second step of drying the aqueous adhesive layer by heating and volatilizing the volatile liquid

And a polarizing plate.

[2] The method for producing a polarizing plate according to [1], wherein at least one of the protective film and the peeling film has a moisture permeability of 400 g / m 2 ∙ 24 hr or more.

[3] The production method of a polarizing plate according to [1] or [2], wherein the peeling film has a shrinkage ratio of 0.15% or less when heated at 80 ° C for 5 minutes.

[4] The method for producing a polarizing plate according to any one of [1] to [3], wherein a contact angle of the polarizing film-side surface of the release film with respect to the volatile liquid is 50 to 80 °.

[5] A method for producing a polarizing plate according to any one of [1] to [4], wherein a contact angle of the polarizing film with respect to the volatile liquid on the side of the release film is 50 to 110 °.

According to the production method of the present invention, it is possible to produce a one-side protective polarizing plate while suppressing the breakage of the polarizing film.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing a basic layer structure of a single-side protection polarizing plate. FIG.
2 is a schematic cross-sectional view showing another example of the single-side polarizing polarizing plate.
3 is a schematic cross-sectional view showing another example of the one-side protective polarizing plate.
4 is a schematic cross-sectional view showing a layer configuration of a double-side protective polarizing plate obtainable by using a single-side protective polarizing plate.
5 is a side view schematically showing an example of a manufacturing method of a single-sided protective polarizing plate and a manufacturing apparatus used therefor according to the present invention.

The present invention relates to a method for producing a single-side protective polarizer. The term " single-side protective polarizing plate " in the present invention is a polarizing plate obtained by bonding a protective film to only one side of a polarizing film, and this protective film is usually bonded to the polarizing film through an adhesive layer. Fig. 1 shows a basic configuration of a single-side protective polarizing plate. 1, the single-sided protective polarizing plate according to the present invention includes a polarizing film 5 and a first protective film 20 (not shown) bonded to one side of the polarizing film 5 through a first adhesive layer 25 ) As a basic configuration.

As will be described in detail later, in the manufacturing method according to the present invention, a protective film (first protective film) is bonded to one surface of a polarizing film through an aqueous adhesive layer, and a layer And a second step of volatilizing the volatile liquid while drying the aqueous adhesive layer by heating. The single-sided protective polarizing plate obtained through the first and second steps may be a single- , And a release film 10 laminated on the other side of the polarizing film 5 like the one side protective polarizing plate 2 with the release film shown in Fig.

The peeling film 10 is a film which can be peeled off from the polarizing film 5 and is peeled off when necessary (for example, when the single-side protective polarizing plate is bonded to the liquid crystal cell) Can be obtained. For example, in order to bond the liquid crystal cell to the liquid crystal cell, the single-sided protective polarizing plate according to the present invention has the pressure-sensitive adhesive layer 30 laminated on the other side of the polarizing film 5, As shown in FIG.

The single-sided protective polarizing plate 1 and the single-sided protective polarizing plate 2 with a peeling film according to the present invention can also be suitably used as an intermediate for manufacturing a double-side protective polarizing plate in which a protective film is bonded to both surfaces of a polarizing film. , The second protective film 21 is bonded to the surface of the polarizing film 5 opposite to the first protective film 20 through the second adhesive layer 26 to form the double-side protective polarizing plate 4 Can be obtained.

Hereinafter, with reference to Fig. 5, a method of manufacturing a single-sided polarizing polarizing plate according to the present invention will be described in detail with reference to embodiments. A method for manufacturing a single-side polarizing polarizer according to the present invention comprises the steps of:

(1) a first step of joining a first protective film to one side of a polarizing film through an aqueous adhesive layer and laminating a peeling film on the other side of the polarizing film through a layer made of a volatile liquid, and

(2) a second step of drying the aqueous adhesive layer by heating and volatilizing the volatile liquid

.

5 is a side view schematically showing one example of a manufacturing method of a single-sided polarizing polarizing plate and a manufacturing apparatus used therefor according to the present invention. In general, a polarizing plate such as a one-side polarizing polarizing plate can be continuously produced as an elongated product by carrying out processing in each step while continuously feeding and transporting a long film as shown in Fig. However, the production method of the present invention is not limited to continuous production using such a long film, and may be a method using a sheetfilm.

(1) First step

5, in this step, a roll (wound product) of a long polarizing film 5, a roll of a long first protective film 20 and a roll of a long peeling film 10 are prepared, The film is transported while being loosened continuously by using a releasing device (not shown). Each film is transported so that its longitudinal direction is the transport direction. A guide roll 60 for supporting a running film is provided on the conveying path of the film appropriately. Arrows in Fig. 5 indicate the transport direction of the film or the rotation direction of various rolls. The transport direction (film length direction) of the polarizing film 5 and the transport direction (film length direction) of the first protective film 20 and the transport direction (film length direction) of the release film 10 are parallel.

In this step, the first protective film 20 is bonded to one side of the polarizing film 5 through the first adhesive layer 25 (not shown in Fig. 5) which is an aqueous adhesive layer, The release film 10 is laminated on the other surface of the substrate 5 through a layer made of the volatile liquid 50. [ As shown in Fig. 5, the first protective film 20, the polarizing film 5, and the peeling film 10 are laminated in such a manner that their lengths The film can be stacked by the bonding rolls 40 and 40 from the upper and lower sides by passing them between the pair of bonding rolls 40 and 40 in a stacked manner so that the direction (conveying direction) becomes parallel.

At this time, just before passing between the bonding rolls 40 and 40, an aqueous adhesive 55 is injected between the polarizing film 5 and the first protective film 20 using the injection devices 80 and 81 A volatile liquid 50 is injected between the polarizing film 5 and the peeling film 10 to form a layer (first adhesive layer 25) composed of an aqueous adhesive 55 and a volatile liquid 50 may be interposed between the layers.

The apparatus for interposing the layer made of the water-based adhesive 55 (the first adhesive layer 25) and the layer made of the volatile liquid 50 is limited to the injection apparatuses 80 and 81 shown in Fig. 5 But not limited to, a coating method such as a doctor blade method, a wire bar coating method, a die coating method, a comma coater method, a gravure coating method, a dip coating method, and a flow-through method depending on the viscosity of the aqueous adhesive 55 and the volatile liquid 50 And the aqueous adhesive 55 and the volatile liquid 50 may be coated on the bonding surfaces of at least one of the films that are overlapped with each other.

There has been a problem that the polarizing film tends to break during the process of producing the single-sided protective polarizing plate because of the fact that the conventional single-polarity protective polarizing plate has been directly laminated on the polarizing film surface without interposing a special layer thereon. In the case where the protective film is bonded to one side of the polarizing film through the water-based adhesive layer, a step of drying the water-based adhesive layer is required in order to obtain the single-side protective polarizing plate. In the conventional manufacturing method, It was easy to break.

According to the manufacturing method of the present invention in which the release film 10 is laminated on the polarizing film 5 with the layer made of the volatile liquid 50 interposed between the polarizing film 5 and the release film 10, The breaking of the polarizing film 5 can be effectively suppressed even in the step of drying the layer (the first adhesive layer 25) made of the adhesive 55 (the second step). The interposition of the layer made of the volatile liquid 50 between the polarizing film 5 and the peeling film 10 also has the effect of suppressing the occurrence of wrinkles in the single-side protective polarizing plate during the process of manufacturing the single-side protective polarizing plate.

Since the intervening volatile liquid 50 can volatilize during the step of drying the first adhesive layer 25 (the second step), in the manufacturing method of the present invention, the volatile liquid 50 No separate process is required.

The bonding surface of the polarizing film 5 and / or the first protective film 20 may be subjected to a plasma treatment, a corona treatment , An ultraviolet ray irradiation treatment, a frame (flame) treatment, and a saponification treatment. Among these, plasma treatment, corona treatment or saponification treatment is preferably performed. For example, when the first protective film 20 is made of a ring-shaped polyolefin-based resin, the bonding surface of the first protective film 20 can be subjected to a plasma treatment or a corona treatment. When the first protective film 20 is made of a cellulose ester resin, the bonding surface of the first protective film 20 can be saponified. As the saponification treatment, a method of immersing in an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide may be mentioned.

[Polarizing Film]

The polarizing film (5) may be one in which a dichroic dye is adsorbed and aligned on a uniaxially stretched polyvinyl alcohol resin film. As the polyvinyl alcohol resin constituting the polyvinyl alcohol resin film, saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include (meth) acrylamides having unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and ammonium groups.

In the present specification, "(meth) acryl" means at least one selected from acrylic and methacrylic. The same applies to "(meth) acryloyl" and "(meth) acrylate".

The saponification degree of the polyvinyl alcohol resin may be in the range of 80.0 to 100.0 mol%, preferably 90.0 to 99.5 mol%, and more preferably 94.0 to 99.0 mol%. When the degree of saponification is less than 80.0 mol%, the water resistance and heat and humidity resistance of the resulting single-sided protective polarizing plate are lowered. When a polyvinyl alcohol resin having a degree of saponification of more than 99.5 mol% is used, the dyeing speed is delayed and the productivity is lowered, and the polarizing film 5 having sufficient polarization performance may not be obtained in some cases.

The degree of saponification indicates the unit ratio (mol%) of the ratio of the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin as the raw material of the polyvinyl alcohol resin to the hydroxyl group by the saponification process , The following formula:

Saponification degree (mol%) = 100 占 (number of hydroxyl groups) / (number of hydroxyl groups + number of acetic acid groups)

. The saponification degree can be obtained according to JIS K 6726 (1994). The higher the degree of saponification, the higher the proportion of hydroxyl groups, and thus the lower the proportion of acetic acid groups that inhibit crystallization.

The average degree of polymerization of the polyvinyl alcohol resin is preferably 100 to 10,000, more preferably 1,500 to 8,000, and still more preferably 2,000 to 5,000. The average degree of polymerization of the polyvinyl alcohol resin can also be determined in accordance with JIS K 6726 (1994). When the average degree of polymerization is less than 100, it is difficult to obtain a desired polarizing performance. When the average degree of polymerization is more than 10,000, the solubility in a solvent deteriorates and it becomes difficult to form a polyvinyl alcohol resin film.

The dichroic dye contained (adsorbed orientation) in the polarizing film 5 may be iodine or a dichroic organic dye. Specific examples of the dichroic organic dyes include red BR, red LR, red R, pink LB, rubin BL, Borde GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy RY, green LG, violet LB, B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Kongogred, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, , Direct First Orange S, and First Black. As the dichroic dye, only one kind may be used alone, or two or more kinds may be used in combination.

The polarizing film (5) comprises a step of uniaxially stretching a polyvinyl alcohol-based resin film; Dyeing a polyvinyl alcohol resin film with a dichroic dye to adsorb the dichroic dye; A step of treating a polyvinyl alcohol-based resin film adsorbed with a dichroic dye with an aqueous solution of boric acid; And a step of washing with water after treatment with an aqueous boric acid solution.

The polyvinyl alcohol-based resin film is a film of the aforementioned polyvinyl alcohol-based resin. The film-forming method is not particularly limited, and known methods such as a melt extrusion method and a solvent casting method can be adopted. The thickness of the polyvinyl alcohol-based resin film is, for example, about 10 to 150 mu m.

The uniaxial stretching of the polyvinyl alcohol resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. When uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. In addition, uniaxial stretching may be performed in a plurality of such steps.

In the uniaxial stretching, stretching may be uniaxially stretched between rolls having different circumferential ratios, or uniaxial stretching may be performed using hot rolls. The uniaxial stretching may be dry stretching in which the stretching is performed in the atmosphere, or may be a wet stretching in which the stretching is performed in a state in which the polyvinyl alcohol resin film is swollen with a solvent. The stretching magnification is usually about 3 to 8 times.

As a method for dyeing a polyvinyl alcohol resin film with a dichroic dye, for example, a method of immersing a polyvinyl alcohol resin film in an aqueous solution (dyeing solution) containing a dichroic dye is adopted. The polyvinyl alcohol-based resin film is preferably subjected to an immersion treatment (swelling treatment) with respect to water before the dyeing treatment.

When iodine is used as the dichroic dye, a method of dying and dyeing a polyvinyl alcohol resin film into an aqueous solution containing iodine and potassium iodide is generally adopted. The content of iodine in the dyeing aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the dyeing aqueous solution is usually about 20 to 40 캜. The immersion time (dyeing time) for the dyeing aqueous solution is usually about 20 to 1800 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of dying and dyeing a polyvinyl alcohol resin film into a dyeing aqueous solution containing a water-soluble dichroic organic dye is generally adopted. The content of the dichroic organic dye in the dyeing aqueous solution is usually about 1 × 10 ^-4 to 10 parts by weight per 100 parts by weight of water, and is preferably about 1 × 10 ^{-3 to} 1 part by weight. The dyeing aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the dyeing aqueous solution is usually about 20 to 80 캜. The immersion time (dyeing time) for the dyeing aqueous solution is usually about 10 to 1800 seconds.

The boric acid treatment after dyeing with the dichroic dye can be carried out by immersing the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid.

The amount of boric acid in the boric acid-containing aqueous solution is generally about 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye, it is preferable that the aqueous solution containing boric acid contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is generally about 0.1 to 15 parts by weight, preferably about 5 to 12 parts by weight, per 100 parts by weight of water. The immersion time for the boric acid-containing aqueous solution is usually about 60 to 1200 seconds, preferably about 150 to 600 seconds, more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 占 폚 or higher, preferably 50 to 85 占 폚, and more preferably 60 to 80 占 폚.

The polyvinyl alcohol resin film after boric acid treatment is usually subjected to water washing treatment. The water washing treatment can be carried out, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of the water in the water washing treatment is usually about 1 to 40 캜. The immersion time is usually about 1 to 120 seconds.

After washing with water, a drying treatment is carried out to obtain a polarizing film (5). There are various methods such as a method of spraying hot air, a method of bringing into contact with hot roll, a method of heating with an IR heater, and any method can be suitably used. The method of bringing the film into contact with the heated roll is preferable in that the drying efficiency can be improved and therefore the drying time can be shortened and the film can be prevented from shrinking in the width direction to widen the film. The drying temperature in the drying step means the atmospheric temperature in the drying furnace in the case of a drying apparatus in which a drying furnace is installed, such as a method of spraying hot air or an IR heater, and in the case of a contact- Surface temperature of the hot roll.

The temperature of the drying treatment is usually about 30 to 100 占 폚, preferably 50 to 80 占 폚. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. The thickness of the polarizing film 5 is usually about 2 to 40 mu m.

By the drying treatment, the water content of the polarizing film 5 is reduced to a practically acceptable level. The water content thereof is usually adjusted to 5 to 45 wt%, more preferably 8 to 40 wt%. If it is lower than 5% by weight, the flexibility of the polarizing film 5 is lost, and the polarizing film 5 may be damaged or broken after drying. When the polarizing film 5 is higher than 45% by weight, It is difficult to sufficiently manifest and problems such as defective appearance and film breakage in the line and pollute the process are likely to occur.

[First protective film]

The first protective film 20 may be formed of a thermoplastic resin, for example, a polyolefin resin such as a chain-like polyolefin-based resin (polypropylene-based resin), a cyclic polyolefin-based resin (norbornene-based resin or the like); Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; Polycarbonate resin; (Meth) acrylic resins such as methyl polymethacrylate resins; Or a mixture or copolymer thereof, or the like.

Examples of the chain-like polyolefin-based resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more kinds of chain olefins. More specifically, examples thereof include a polypropylene resin (a polypropylene resin which is a homopolymer of propylene or a copolymer mainly comprising propylene), a polyethylene resin (a polyethylene resin which is a homopolymer of ethylene or a copolymer mainly comprising ethylene) .

The cyclic polyolefin-based resin is a generic name of resins polymerized by using cyclic olefin as a polymerization unit, and examples thereof include those described in JP-A-1-240517, JP-A-3-14882, JP-A-3-122137 And resins described in, for example, JP-A-2004-346991. Specific examples of the cyclic polyolefin-based resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene (typically, random copolymers ), Graft polymers obtained by modifying these with unsaturated carboxylic acids or their derivatives, and hydrides thereof. Of these, norbornene-based resins using norbornene monomers such as norbornene and polycyclic norbornene-based monomers as the cyclic olefins are preferably used.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. These copolymers and those obtained by modifying a part of hydroxyl groups with other substituents may also be used. Of these, cellulose triacetate (triacetylcellulose: TAC) is particularly preferable.

The polyester-based resin is a resin having an ester bond and is generally composed of a polycondensation product of a polycarboxylic acid or a derivative thereof and a polyhydric alcohol. As the polycarboxylic acid or its derivative, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethylterephthalate, dimethyl naphthalenedicarboxylate and the like. As the polyhydric alcohol, a dihydric diol can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol. Examples of suitable polyester-based resins include polyethylene terephthalate.

The polycarbonate resin is an engineering plastic made of a polymer having a monomer unit bonded through a carbonate group, and is a resin having high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate resin may be a resin called a modified polycarbonate such as a polymer skeleton modified to lower the photoelastic coefficient or a copolymerized polycarbonate improved in wavelength dependency.

The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of the (meth) acrylic resin include poly (meth) acrylic acid esters such as polymethyl methacrylate; Methyl methacrylate- (meth) acrylic acid copolymer; Methyl methacrylate- (meth) acrylic acid ester copolymer; Methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer; (Meth) acrylate-styrene copolymer (MS resin and the like); A copolymer of a compound having an alicyclic hydrocarbon group and methyl methacrylate (e.g., a methyl methacrylate-cyclohexyl copolymer, a methacrylic acid methyl- (meth) acrylate nonyl copolymer, etc.). Preferably, a polymer mainly composed of a poly (meth) acrylate C _1-6 alkyl ester such as poly (meth) acrylate is used, more preferably methyl methacrylate as a main component (50 to 100 wt% By weight, preferably 70 to 100% by weight) is used.

The first protective film 20 may be a protective film having optical functions such as a retardation film and a brightness enhancement film. For example, a retardation film having an arbitrary retardation value can be obtained by stretching (uniaxially stretching or biaxially stretching) a transparent resin film made of the above material, or forming a liquid crystal layer or the like on the film.

A surface treatment layer (coating layer) such as a hard coating layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer may be formed on the surface of the first protective film 20 opposite to the polarizing film 5. The method for forming the surface treatment layer on the surface of the protective film is not particularly limited, and a known method can be used.

The thickness of the first protective film 20 is preferably thin from the viewpoint of thinning of the polarizing plate, but if it is too thin, the strength is lowered and the workability is lowered. Therefore, the thickness of the first protective film 20 is preferably 5 to 90 占 퐉 or less, more preferably 5 to 60 占 퐉, and still more preferably 5 to 50 占 퐉.

The moisture permeability of the first protective film 20 is preferably 400 g / m 2 ∙ 24 hr or more, more preferably 420 g / m 2 ∙ 24 hr or more. When the moisture permeability is within this range, the layer made of the water-based adhesive 55 can be efficiently dried in the subsequent second step, thereby improving the productivity.

[Water-based adhesive]

The water-based adhesive 55 for forming the first adhesive layer 25 is obtained by dissolving the adhesive component in water or dispersing it in water. The water-based adhesive preferably used is, for example, an adhesive composition using a polyvinyl alcohol resin or a urethane resin as a main component. The thickness of the first adhesive layer 25 formed of an aqueous adhesive is usually 1 占 퐉 or less.

When a polyvinyl alcohol resin is used as the main component of the adhesive, the polyvinyl alcohol resin may be a partially saponified polyvinyl alcohol, a completely saponified polyvinyl alcohol, a carboxyl group-modified polyvinyl alcohol, an acetoacetyl group-modified polyvinyl alcohol, Modified polyvinyl alcohol resins such as modified polyvinyl alcohol and amino group-modified polyvinyl alcohol. The polyvinyl alcohol resin may be a polyvinyl alcohol copolymer obtained by saponifying a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate which is a homopolymer of vinyl acetate, as well as a copolymer of vinyl acetate and another monomer copolymerizable therewith .

An aqueous adhesive containing a polyvinyl alcohol resin as an adhesive component is usually an aqueous solution of a polyvinyl alcohol resin. The concentration of the polyvinyl alcohol resin in the adhesive is usually 1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of water.

In order to improve the adhesiveness, it is preferable to add a curing component such as a polyaldehyde, a melamine compound, a zirconia compound, a zinc compound, a glyoxal and a water-soluble epoxy resin or a crosslinking agent to the adhesive composed of an aqueous solution of a polyvinyl alcohol resin . Examples of the water-soluble epoxy resin include epoxy resins obtained by reacting epichlorohydrin with polyamide amines obtained by the reaction of polyalkylene polyamines such as diethylene triamine and triethylene tetramine with dicarboxylic acids such as adipic acid A polyamide polyamine epoxy resin can be suitably used. Examples of commercially available polyamide polyamine epoxy resins include Sumirez Resin 650 (manufactured by Daoka Chemical Industry Co., Ltd.), Sumirez Resin 675 (manufactured by Daoka Chemical Industry Co., Ltd.), WS-525 (Manufactured by Japan PMC Co., Ltd.). The addition amount of these curable components and the crosslinking agent (the total amount when they are added together as the curing component and the crosslinking agent) is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight, relative to 100 parts by weight of the polyvinyl alcohol resin. When the addition amount of the curable component or the crosslinking agent is less than 1 part by weight based on 100 parts by weight of the polyvinyl alcohol resin, the effect of improving the adhesiveness tends to be small. When the addition amount of the curable component or the cross- If the amount is more than 100 parts by weight based on 100 parts by weight of the base resin, the adhesive layer tends to become fragile.

When a urethane resin is used as the main component of the adhesive, examples of suitable adhesive compositions include a mixture of a polyester-based ionomer-type urethane resin and a compound having a glycidyloxy group. The polyester-based ionomer-type urethane resin is a urethane resin having a polyester skeleton in which a small amount of an ionic component (hydrophilic component) is introduced. Such an ionomeric urethane resin is suitable as an aqueous adhesive since it emulsifies directly by emulsification in water without using an emulsifier.

[Peeling film]

The peeling film 10 is a film which can be peeled off at a desired timing after being laminated on the polarizing film 5. Means that the polarizing film 5 and the peeling film 10 can be separated without damaging or damaging the polarizing film 5 and the peeling film 10.

In consideration of handleability, transparency, and cheapness, the release film 10 is preferably made of a polyolefin-based resin such as a polyethylene-based resin or a polypropylene-based resin; Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; A (meth) acrylic resin such as polymethyl methacrylate resin, a mixture thereof, a copolymer thereof, and the like. A film obtained by molding one or more of these materials into a single layer or a multilayer structure may be used as the peeling film 10. Among them, a film made of polyethylene terephthalate, cellulose triacetate and methyl polymethacrylate resin can be suitably used.

The peel force between the polarizing film 5 and the release film 10 is, for example, 0.01 to 0.5 N / 25 mm, preferably 0.01 to 0.2 N / 25 mm, and more preferably 0.01 to 0.15 N / 25 mm . When the peeling force is less than 0.01 N / 25 mm, the adhesion between the polarizing film 5 and the peeling film 10 is small, so that the peeling film 10 is partially peeled off or the single-side protective polarizing plate is kept in a roll- The polarizing film 5 may be torn along the stretching direction (in the direction parallel to the stretching direction). When the peeling force exceeds 0.5 N / 25 mm, it becomes difficult to peel off the peeling film 10 from the polarizing film 5, so that when the peeling film 10 is peeled off, the polarizing film 5 is stretched in the stretching direction It tends to be torn.

Here, the peeling force was obtained by measuring a single-side protective polarizing plate on which the peeling film 10 was laminated, cut to a width of 25 mm, and measuring samples were obtained using an autograph AGS-50NX precision universal testing machine manufactured by Shimadzu Corporation And measuring the force at the time of peeling the film in the direction of 180 by holding the peeling film 10 as the measurement sample and the one-side protective polarizing plate. The peeling force is measured in an environment of a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 5% at a peeling speed of 300 mm / min.

The thickness of the release film 10 is, for example, about 5 to 100 mu m, preferably about 10 to 80 mu m.

The moisture permeability of the release film 10 is preferably 400 g / m < 2 > 24 hr or more, and more preferably 420 g / m < 2 > If the moisture permeability is within this range, the layer made of the volatile liquid 50 can be efficiently volatilized and removed in the subsequent second step, thereby improving the productivity.

The shrinkage percentage (heat shrinkage ratio) of the release film 10 when heated at 80 DEG C for 5 minutes is preferably 0.15% or less, and more preferably 0.1% or less. When the heat shrinkage percentage of the peeling film 10 is large, wrinkles easily occur in the peeling film 10 in the heat treatment in the second step, and wrinkles are likely to occur on the single-side protection polarizing plate. Examples of the resin material having a heat shrinkage ratio within the above range include polyethylene terephthalate, cellulose triacetate, and polymethyl methacrylate resin.

The term " heat shrinkage percentage is 0.15% or less " means that both the MD shrinkage percentage and the TD shrinkage percentage are 0.15% or less.

The contact angle of the side of the polarizing film 5 on the side of the polarizing film 5 with respect to the volatile liquid 50 in the polarizing film 5 is preferably 50 to 80, Of the peeling film 10 is within the above-mentioned range, and the peeling film 10 can be relatively easily peeled off. For the same reason, the contact angle of the polarizing film 5 with respect to the volatile liquid 50 on the side of the release film 10 is preferably 50 to 110 °, more preferably 50 to 100 °.

[Volatile liquid]

The volatile liquid 50 interposed between the polarizing film 5 and the peeling film 10 is a liquid which can be volatilized by the heat treatment in the second step and is preferably a liquid which does not adversely affect the polarizing film 5 It is liquid. If it does not adversely affect, an antistatic agent may be added. Examples of the volatile liquid 50 usable in the present invention are, for example, water or a mixture of water and a hydrophilic liquid. It is preferable that the hydrophilic liquid does not remain after the heat treatment in the second step. For example, the hydrophilic liquid does not remain after the heat treatment in the second step, and examples thereof include methanol, ethanol, 1-butanol, tetrahydrofuran, acetone, acetonitrile, N, , Acetic acid, and the like.

(2) Second step

In this step, the first adhesive layer 25, which is an aqueous adhesive layer, is dried by heating, and the volatile liquid 50 is volatilized and removed. By this heat treatment, the release film 10 is laminated on the surface of the polarizing film 5 with a suitable adhesion force.

5, the heating treatment is performed by moving the laminated film composed of the first protective film 20, the polarizing film 5 and the peeling film 10 passed between the bonding rolls 40 and 40 to the drying device 70 ). Thereby, a single-side protective polarizing plate 2 with a peeling film is obtained. The drying device 70 is not particularly limited, and a hot-air dryer or a far-infrared heater can be used.

The drying temperature is preferably 30 to 90 占 폚. If the temperature is lower than 30 占 폚, the first protective film 20 tends to be easily peeled off from the polarizing film 5 in the obtained single-surface protection polarizing plate 2 with the peeling film. If the drying temperature exceeds 90 DEG C, there is a fear that the polarization performance of the polarizing film 5 is deteriorated by heat. The drying time can be about 10 to 1000 seconds, and from the viewpoint of productivity, it is preferably 60 to 750 seconds, more preferably 150 to 600 seconds.

One of the advantages of the present invention lies in that the heating temperature in this step can be increased to, for example, from about 60 DEG C to about 90 DEG C or less. In other words, even if the heating temperature is set high, not only the breakage of the polarizing film 5 can be suppressed, but also the one-side protective film having a small shrinkage percentage of the polarizing film 5 and hence high dimensional stability is obtained . By reducing the shrinkage ratio of the one-side protective polarizing plate, it is possible to reduce warpage of the liquid crystal panel when the liquid crystal panel is manufactured using this polarizing plate. Conventionally, since the polarizing film is easily broken, the drying temperature of the water-based adhesive layer can not be set high, and it has been difficult to obtain a one-side protective polarizing plate with a low shrinkage ratio.

(3) Other processes

After the second step, a sufficient curing strength may be obtained by curing at least a half day, usually several days or more, at a temperature of room temperature or higher. Such curing is typically carried out in a rolled-up state. The preferred curing temperature is in the range of 30 to 50 占 폚, more preferably 35 to 45 占 폚. When the curing temperature exceeds 50 占 폚, so-called "cyming" tends to occur in the roll state. The humidity at the time of curing is not particularly limited, but is preferably selected so that the relative humidity ranges from 0 to 70% RH. The curing time is usually about 1 to 10 days, preferably about 2 to 7 days.

A third step of peeling off the peeling film 10 from the single side polarizing plate 2 with the peeling film after the second step and a third step of peeling off the peeling film 10 from the single side polarizing plate 2 with the peeling film 10, (30) are laminated on the surface of the polarizing plate (3) to form a single-sided polarizing plate (3) having a pressure-sensitive adhesive layer as shown in Fig. This pressure-sensitive adhesive layer 30 can be used for bonding the one-side protective polarizing plate to the liquid crystal cell.

As the pressure-sensitive adhesive for use in the pressure-sensitive adhesive layer 30, conventionally known pressure-sensitive adhesives can be used. Examples of the pressure-sensitive adhesive include (meth) acrylic pressure sensitive adhesives, urethane pressure sensitive adhesives, silicone pressure sensitive adhesives, polyester pressure sensitive adhesives, polyamide pressure sensitive adhesives, Fluorine-based pressure-sensitive adhesives, and rubber-based pressure-sensitive adhesives. Among them, a (meth) acrylic pressure-sensitive adhesive is preferably used from the viewpoints of transparency, adhesive strength, reliability, reworkability and the like. The pressure-sensitive adhesive layer 30 can be formed by using a pressure-sensitive adhesive in the form of an organic solvent solution, coating it on a polarizing film 5 using a die coater, a gravure coater, or the like, (Hereinafter referred to as " separator film ") on which the polarizing film 5 has been formed is transferred to the polarizing film 5. Whichever method is adopted, it is preferable that the separate film is adhered to the surface of the pressure-sensitive adhesive layer (30). The thickness of the pressure-sensitive adhesive layer 30 may be, for example, 2 to 40 m.

Alternatively, instead of providing the fourth step, the second protective film 21 is bonded to the surface of the polarizing film 5 on which the release film 10 has been laminated, through the second adhesive layer 26, The protective polarizing plate 4 may be obtained. The second adhesive layer 26 may be an aqueous adhesive layer like the first adhesive layer 25, or may be a layer made of another adhesive. Examples of other adhesives include active energy ray-curable adhesives which can be cured by irradiation with active energy rays such as ultraviolet rays, visible rays, electron beams and X-rays. In this case, the second adhesive layer 26 is a cured layer of the adhesive.

The second protective film 21 may be a protective film having optical functions such as a retardation film and a brightness enhancement film. The double-sided protective polarizing plate 4 can be bonded to the liquid crystal cell by using the pressure-sensitive adhesive layer 30 laminated on the outer surface of the first protective film 20 or the second protective film 21.

Among these, as the adhesive forming the second adhesive layer 26, an active energy ray-curable adhesive containing an epoxy compound curable by cationic polymerization as a curable component can more preferably be used, and more preferably, Based compound as a curable component. The epoxy compound referred to herein means a compound having an average of at least one, preferably two or more epoxy groups in the molecule. The epoxy compound may be used alone, or two or more epoxy compounds may be used in combination.

Examples of suitable epoxy compounds include a hydrogenated epoxy compound obtained by reacting an alicyclic polyol obtained by subjecting an aromatic ring of an aromatic polyol to a hydrogenation reaction with epichlorohydrin (a glycidyl group of a polyol having an alicyclic ring Diesters); Aliphatic epoxy compounds such as polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof; And an alicyclic epoxy compound which is an epoxy compound having at least one epoxy group bonded to an alicyclic ring in the molecule.

The active energy ray-curable adhesive may further contain a (meth) acrylic compound that is radically polymerizable as a curable component. Examples of the (meth) acrylic compound include (meth) acrylate monomers having at least one (meth) acryloyloxy group in the molecule; (Meth) acryloyloxy group-containing compounds such as (meth) acrylate oligomers obtained by reacting two or more kinds of functional group-containing compounds and having at least two (meth) acryloyloxy groups in the molecule.

When the active energy ray-curable adhesive contains an epoxy compound curable by cationic polymerization as a curable component, it preferably contains a photocationic polymerization initiator. Examples of the cationic polymerization initiator include aromatic diazonium salts; Onium salts such as aromatic iodonium salts and aromatic sulfonium salts; Iron-allene complexes and the like. Further, when the active energy ray-curable adhesive contains a radically polymerizable curable component such as a (meth) acrylic compound, it preferably contains a photo radical polymerization initiator. Examples of the photo radical polymerization initiator include an acetophenone-based initiator, a benzophenone-based initiator, a benzoin ether-based initiator, a thioxanthone-based initiator, xanthone, fluorenone, camphorquinone, benzaldehyde and anthraquinone.

When an active energy ray-curable adhesive is used, a curing step for curing the adhesive layer made of the active energy ray-curable adhesive is performed. The curing of the adhesive layer can be performed by irradiating an active energy ray. The active energy ray is preferably ultraviolet ray.

A light source of an active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, a low energy mercury lamp, medium pressure mercury lamp, high pressure mercury lamp, ultra high pressure mercury lamp, A wave excitation mercury lamp, a metal halide lamp and the like are preferably used.

The active energy ray irradiation intensity for the adhesive layer made of the active energy ray curable adhesive is appropriately determined according to the composition of the adhesive but is set so that the irradiation intensity in the wavelength range effective for activating the polymerization initiator is 0.1 to 6000 mW / . When the irradiation intensity is not less than 0.1 mW / cm 2, the reaction time does not become excessively long, and when the irradiation intensity is 6000 mW / cm 2 or less, the heat radiated from the light source and the heat of curing of the adhesive, There is little possibility of deterioration.

The irradiation time of the active energy ray is suitably determined according to the composition of the adhesive, but it is preferable that the accumulated light amount expressed as the product of the irradiation intensity and the irradiation time is set to 10 to 10,000 mJ / cm 2. When the accumulated light quantity is 10 mJ / cm 2 or more, a sufficient amount of active species originating from the polymerization initiator can be generated sufficiently to progress the curing reaction more surely. When the total light quantity is 10,000 mJ / cm 2 or less, the irradiation time is not excessively long, .

With respect to the material and the constitution of the second protective film 21, the description about the first protective film 20 is cited. The first protective film 20 and the second protective film 21 may be the same kind of film or different kinds of films.

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The moisture permeability, shrinkage, contact angle and peeling force in the following examples were measured according to the following methods.

(1) Water vapor permeability of protective film and peeling film

The moisture permeability (g / m < 2 > 24 hr) at 40 DEG C was measured in accordance with JIS Z 0208.

(2) Shrinkage percentage of release film

A specimen having a square of 100 mm on one side was cut out from the peel film so that one side was in parallel with the MD (film length direction) of the peel film, and the initial size A (initial dimension of MD) From the dimension B (dimension of MD) after holding for 5 minutes under a dry heat environment of the following formula:

MD dimensional change rate (%) = (A-B) / A x 100

To calculate the MD dimensional change ratio of the peeled film, and this was taken as the MD shrinkage percentage. In the same manner, the TD dimensional change ratio is calculated from the initial dimension A '(the initial dimension of TD) and the dimension B' (TD dimension) after holding the test piece under a dry heat environment of 80 ° C for 5 minutes. did.

(3) Contact angle of polarizing film and peeling film surface

The polarizing film or the peeling film was bonded to the glass substrate using a pressure-sensitive adhesive, with the measurement object side (the side of the release film side in the polarizing film or the side of the polarizing film in the release film) outside, and used as a measurement sample. This measurement sample was horizontally set on a contact angle meter (image processing contact angle meter "FACE CA-X type" manufactured by Kyowa Interface Science Co., Ltd.) such that the surface to be measured was the upper surface, and 1 microliter The volatile liquid was dropped to measure the contact angle with respect to the volatile liquid.

(4) peeling force between the polarizing film and the peeling film

The peeling force was measured by cutting a single-side protective polarizing plate on which a peeling film was laminated by cutting to a width of 25 mm to obtain a measurement sample. Using a precision universal testing machine "Autograph AGS-50 NX" manufactured by Shimadzu Corporation, Peeling film and the one-side protective polarizing plate and measuring the force at the time of peeling in the direction of 180 DEG. The peeling force was measured in an environment of a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 5% at a peeling speed of 300 mm / min.

≪ Example 1 >

(A) Production of polarizing film

A polyvinyl alcohol film having an average degree of polymerization of about 2400, a degree of saponification of 99.9 mol% or more and a thickness of 30 탆 was uniaxially stretched by about 4 times in a dry state and immersed in pure water at 40 캜 for one minute while maintaining the tension, / Potassium iodide / water at a weight ratio of 0.1 / 5/100 at 28 ° C for 60 seconds. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 10.5 / 7.5 / 100 at 68 ° C for 300 seconds. Subsequently, the film was washed with pure water at 5 占 폚 for 5 seconds, and then dried at 70 占 폚 for 180 seconds to obtain a polarizing film in which iodine was adsorbed and aligned on the uniaxially stretched polyvinyl alcohol film. The thickness of the polarizing film was 11 mu m.

(B) Preparation of aqueous adhesive

A polyvinyl alcohol aqueous solution having a concentration of 3% by weight was prepared by dissolving a polyvinyl alcohol powder (trade name: "KL-318" manufactured by Kuraray Co., Ltd., average degree of polymerization: 1800) in hot water at 95 ° C. A water-based adhesive was prepared by mixing 1 part by weight of a crosslinking agent (Sumirez Resin 650, manufactured by Daoka Chemical Industry Co., Ltd.) with 2 parts by weight of polyvinyl alcohol powder.

(C) Production of single-side protective polarizer with peeling film

Using the same apparatus as that of the polarizing plate producing apparatus shown in Fig. 5, a single-side polarizing protective polarizing plate with a peeling film was produced in the following order. The polarizing film obtained in the above step (A) was continuously transported and a roll of a protective film (trade name "KC2UAW", trade name, manufactured by Konica Minolta Opto, Inc., thickness 25 μm, And the release film was continuously unwound from a roll of a release film (TAC film manufactured by Konica Minolta Opto, Inc., trade name " KC8UX2MW ", thickness: 80 mu m, not saponified). Subsequently, the water-based adhesive obtained in the above (B) is injected between the polarizing film and the protective film, and pure water is injected between the polarizing film and the peeling film and passed between the bonding rolls 40 and 40, Adhesive layer / polarizing film / pure water / release film (first step). Subsequently, the laminated film is conveyed, passed through the drying device 70, and subjected to heat treatment at 80 DEG C for 300 seconds to remove the pure water interposed between the polarizing film and the peeling film by volatilization , A single-side protective polarizing plate with a peeling film was obtained (second step).

During the production of the single-side protective polarizing plate with the peeling film, no breakage of the polarizing film nor wrinkles of the polarizing plate occurred. Table 1 shows the measurement results of the moisture permeability, shrinkage and logarithmic contact angle of the polarizing film, protective film or peeling film used. Table 1 also summarizes the breakage of the polarizing film and the occurrence of wrinkles of the polarizing plate during the production of the single-side protective polarizing plate with a peeling film.

With respect to the obtained single-side protective polarizing plate with a peeling film, the peeling force between the polarizing film and the peeling film was measured according to the above-mentioned measuring method and found to be 0.10 N / 25 mm.

≪ Examples 2 to 11, Comparative Examples 1 and 2 >

A single-side protective polarizing plate with a peeling film was produced in the same manner as in Example 1, except that the kind of the protective film and the kind of the peeling film were changed as shown in Table 1. In Comparative Examples 1 and 2, in the first step, the peeling film was directly laminated on the polarizing film surface without interposing pure water between the polarizing film and the peeling film.

In the same manner as in Example 1, the results of measurement of the moisture permeability, shrinkage percentage, and logarithmic contact angle of the polarizing film, protective film or peeling film used, and the occurrence of the polarizing film breakage and the wrinkles of the polarizing plate during the production of the single- Table 1 together. The abbreviations in Table 1 are as follows.

[A] TAC 1: a trade name "KC2UAW", a TAC film manufactured by Konica Minolta Opto, thickness: 25 μm, a surface subjected to saponification treatment,

[B] COP: a trade name " FEKB015D3 ", a cyclic polyolefin-based resin film manufactured by JSR Corporation,

[C] PET: A polyethylene terephthalate film of Mitsubishi Resin Co., Ltd., thickness of 25 탆,

[D] Acrylic 1: Polymethylmethacrylate resin film of Sumitomo Chemical Co., Ltd., thickness: 40 占 퐉,

[E] TAC 2: a trade name " KC8UX2MW ", which is a TAC film manufactured by Konica Minolta Opto, thickness 80 μm, not saponified,

[F] PE: trade name " Toray Tek 7332K ", polyethylene film of TORAY FILM PROCESSING CO., LTD.

[G] Acrylic 2: Polymethylmethacrylate resin film of Sumitomo Chemical Co., Ltd., thickness 80 占 퐉,

[H] EtOH: ethanol.

As shown in Table 1, in Examples 1 to 11, since the volatile liquid was interposed between the polarizing film and the peeling film, the polarizing film did not break even after the heat treatment at 80 캜. In contrast, in Comparative Examples 1 and 2 in which no volatile liquid was interposed, the polarizing film was broken by the heat treatment at 80 캜. In Examples 9 and 10 using a release film having a large shrinkage percentage with a volatile liquid interposed between the polarizing film and the release film, the polarizing plate was wrinkled by heat treatment at 80 占 폚.

1: one side protective polarizing plate, 2: one side protective polarizing plate with a peeling film, 3: one side protective polarizing plate with a pressure sensitive adhesive layer, A second adhesive layer, and a second adhesive layer. The adhesive layer includes a first adhesive layer, a second adhesive layer, and a second adhesive layer. 81: Injection device.

Claims (5)

A first step of bonding a protective film to one side of the polarizing film through an aqueous adhesive layer and laminating a release film on the other side of the polarizing film through a layer made of a volatile liquid,
A second step of drying the aqueous adhesive layer by heating and volatilizing the volatile liquid
And a polarizing plate. The method of producing a polarizing plate according to claim 1, wherein at least one of the protective film and the release film has a moisture permeability of 400 g / m < 2 > The method for producing a polarizing plate according to claim 1 or 2, wherein the peeling film has a shrinkage ratio of 0.15% or less when heated at 80 캜 for 5 minutes. The method of manufacturing a polarizing plate according to any one of claims 1 to 3, wherein a contact angle of the polarizing film side surface of the peelable film with respect to the volatile liquid is 50 to 80 °. The method of manufacturing a polarizing plate according to any one of claims 1 to 4, wherein a contact angle of the peeling film-side surface of the polarizing film with respect to the volatile liquid is 50 to 110 °.

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